Hydraulic System Preventive Maintenance

Most of the production personnel carry the impression that a maintenance department exists primarily to repair the faults that occur. Unfortunately this is not the case. The most important part of the maintenance department’s responsibility is to perform routine planned maintenance otherwise known as preventive maintenance.

Preventive maintenance primarily deals with:
• Regular servicing of the equipment
• Checking for correct operation
• Identification of potential faults and their immediate rectification or correction.

As an often-overlooked side benefit, planned maintenance trains the maintenance technician in the proper operation and layout of the plant for which they are responsible. Most of the common problems listed in the introductory section of this chapter can be eliminated if a planned preventive maintenance program is undertaken.

More than 50% of the problems encountered in hydraulic systems have been observed to be related to hydraulic oil. This is why regular sampling and testing of the hydraulic fluid is a very important. A portable hydraulic fluid test kit is available nowadays. This helps in carrying out the basic tests at the site itself. Tests that can be performed include ones such as determination of viscosity, water content and particulate contamination.

It is vital that the maintenance personnel be trained to carry out maintenance activities effectively. A technician should also be able to recognize the early symptoms of potential hydraulic problems. For example, a noisy pump may be due to cavitation caused by a clogged inlet filter. It might also be due to a loose inlet fitting which permits air ingress
into the pump. If the cavitation is due to air leakage in the pump, the oil in the reservoir tends to get covered with foam. When air becomes entrained in the oil, it causes spongy operation of the hydraulic actuators. A sluggish actuator may also be due to the high viscosity of the fluid.

good reporting and recording system. These reports should include the following:
• The type of symptoms encountered and how they were detected along with the respective date
• A description of the maintenance repairs performed. This should include the replacement of parts, the amount of downtime and the date
• Records of dates when the oil was tested, added or changed
• Records of dates when the filters were cleaned or replaced.

Proper maintenance procedures with respect to external oil leakages are also essential. Safety hazards due to oil spillage on the floor should be prevented. The bolts and brackets of loose mountings should be tightened as soon as they are detected as they can cause misalignment of the pump and actuator shafts.

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